Ideally, toned images on a transfer member would be fully transferred off and then no subsequent cleaning would be needed. In practice, however, cleaning is common, often by scraping the residual toner off with a blade which contacts the toned surface. When the surface of the toned member is soft, as is typically true for intermediate transfer members, such mechanical cleaning, causes physical wear which shortens the useful life of the toned member.
This invention employs an electrically biased cleaner, the electrical bias being the essential force moving toner from the toned member to an endless cleaning member. Use of electrical bias for removal of toner in cleaning is disclosed in U.S. Pat. Nos. 5,119,144 to Hada et al, 5,241,343 to Nishio and 5,034,778 to Levanon et al (the cleaning roller 56 being only at electrical ground). In the Hada et al disclosure a second, pushing electrical bias is produced from the inside of the photoconductor.
Such prior art appears to rely significantly on some physical rubbing action of the cleaning member. Thus, in the Hada patent the cleaning member is shown as bristles and in the Nishio patent the cleaning member is a foam roller. In Levanon et al the cleaning roller 56 is rotated to move opposite to the surface of the photoconductor being cleaned. No prior art is known to produce highly complete cleaning with minimal wear on the toned member as does this invention.
The wick applicator of silicone oil of the preferred embodiment of this invention is identical in structure with that used to apply silicon oil otherwise identical to that of the preferred embodiment of this invention but of a higher nominal viscosity to a transfer roller in prior art printers sold by the assignee of this invention. Since such transfer roller is heated, the actual viscosity of the oils in this invention and of the prior art are intended to be substantially identical. That prior art use, however, does not involve cleaning employing an electrified member.